Titanium-aluminum alloys



United States Patent Ofi" Patented Mar. 31, 1959 1 1 2,880,087 TITANIUM-ALUMINUM ALLOYS Robert I. Jatfee, Worthington, Ohio, assignor, by mesne assignments, to Crucible Steel Company of America,

Flemington, N.J., a corporation of New Jersey No Drawing. ApplicationJanuary18,?1957 Serial No. 634,813 .13 Claims. (Cl. 75-1755) mcember. 22, 1948, and now. abandoned,--a'nd isalso a :ycontinuation-impartof copending application SerialNo. 1545,121,.,fi1ed October 24, 1955, which is-in turn a continuation-in-part of application Serial No. 392,052y filed November v13, 1953, and nowabandoned.

zThe metal titanium at ordinary temperatures=is of a close-packed hexagonal structure 1 commonly ealledl the alpha phase. At a temperature .of about 885 .Cs, it is transformed to a body-centered cubic structure known as the beta phase. The addition of aluminum tends to stabilize the alpha'phase. Our investigations have estab- -lished that titanium-aluminum binaryalloys containing up to 25% aluminum are found to consist entirely of equiaxed alpha grains. When the aluminumcontent is increased to about 30% another phase appears interspersed with the'alpha phase in a plate-like structure. This additional phase is not beta titanium but a third '-crystalline form which, due to its high aluminumcontent, cannot be called a phase of titanium.- Forthe purpose of this specification, it will beidentified as I(A1Ti). -Its crystalline form is face-centered tetragonal. When ,.the aluminum content isincreased to about 32%, alpha titanium is still present, but at an aluminumcontent of about 34%, thealpha titanium disappears, and the entire microstructure is one of equiaxed I(A1Ti) .grains. ,A .photomicrograph shows a strong resemblancev to many -of,the brasses. As thealuminum content .is furtherincreased, the alloy continues single phase I(AlTi) up to an aluminum contentof about 46% At analuminnm content. of about 50%, thealloy againhas a two-phase microstructure.

In the previously filed applications referred.to,.,. we

such'as carbonysilvengermanium andzirconium. I have also discovered thatsuch additions greatly increase" the strength-and ductilitysofuthese alloys at both room-and elevated-temperatures.

Carbon is beneficial .up to about 0.3% with aluminum up to--about silver, germanium: and zirconium-' are e beneficial jup to'about 5%"with-'aluminummpto"at least 1.:10-15%. Thelower 'efiectiveslimit for-carbon isabout 0.05%' and for Ag, Ge, and Zr about 0.5%.

Of: the beta I promoters, ithose of the =beta-isomorph0us 1 group--Mo, V, Cb :and .Ta, 'z'especi'ally vanadium, are

. effective-up to-40%'-or more. FTheeutectoid beta' pro- Hmoters such iasMn, Fe, Co,-Ni, Cu,.etc.',nparticularly Qmanganese and copper,-are etfective up to; about':10-'15% with aluminum up toi-ab0ut,'5l5%. The lower ielfective ,limit, forthe beta promoters: is about 0.5%.

aOf the interstitialswcarbon; oxygen-and nitrogen,;only

- :carbon is arbeneficial'additionupito about 0.3%.:2151'1'6- I gards improvement in r hot; workability and strengthfiof :the high aluminum, Ti Al alloysof the inventions Nitro- 1- gen and oxygen in amounts of 0.1 each impair rhot workability. Of the alpha-pr.omoters, Esilverin amounts peratures ".of' ty]; iCal alloys-according -to' the*in-vention. In this tabulation, the specimens are rated as follows according to-forgeability and rollability at theindicated Wforging or .rolling temperatures, to wit: -G=good;

have shown that titanium-aluminum alloys containing 8% and under of alum-inum-are sufficiently ductile to be hot and cold formed as by forging, rolling; drawing,etc., and thatthey also possess relatively high-strength, particularly in the range of about 2.5 to 8% aluminum. As ,was further shown in said earlier applications, as the \aluminum content is increased above 8%, the binary titanium-aluminum alloys become increasingly brittle, but can be fabricated by hot working up to at least 12% aluminum, and are usable in cast form for higher 'aluminum contents. It was further shown that these hot workable alloys containing from more than 8% up to "at least 12% aluminum have -very desirable hot hardness properties.

I have further discovered that the hot workability of titanium-aluminum alloys containing from more than 8% up to about 34% aluminum is greatly improved by additions of one or more of the beta-stabilizing elements Mo, V, Cb, Ta, Mn, Cr, Fe, W, Co, Ni,Cu, Si and Be,

F=fair; P=poor; N-G=wholly tunfabricable.

TABLE I Fabrication ratings of T i.Al and Ti--Al X alloys containing over 8% Al Forging Rolling As Cast Composition, -Hard- Percent 1 ness, i (Balance Titanium) Tgnfi p Rating Tslgp Rating .VHN

10A1 1, 800 P 1, 700 F-P i 10Al0.250 1, 600 F-G j.12.5Al-0.25O 1,800 N-G 10Al-2Cu 1, 800 GF l, 700 NG 10A1-4Cu l- 1, 800 G 1, 700 G-F 10Al5Cu- 2. 000 G-F l, 700 G 10Al-60u- -1, 800' G 1,700 G 12111-4011- 1, 800 G 1,700 P 12A1-6Cu 1, 800 G 1, 700 G-F 12Al-8Cu- 1, 800 G 1, 700 G l2Al-l20u 1, 800 F l, 700 F 14Al-40u- 1, 800 F-P 1, 700 N-G MAI-60o. 1, 800 F-P 1, 700 N-G 15Al10Cu 1, 800 N-G 1, 700 N-G 30Al5Cu 1, 800 N G 1, 700 N-G l0Al-5Ag 1, 800 P 1, 700 P-N-G 10Al5Nl l, 800 G 1, 700 G ..10Al5V 1, 800 G 1, 700 1 G'F 10Al50o. 1, 800 G 1, 700 G 10Al-5Mn- 1, 800 G l, 700 G 10Al-5Mo 1, 800 G-F l, 700 G-F 10A12.5Fe- 1, 800 G 10Al-5Fe.- 1,800 G .10Al2.5Ag 1,800 F 1, 600 F 10Al-5Ag 1, 800 N-G 10Al-2 5Mo-0.250 1, 600 N-G 10Al-2.5Ge 1, 800 G l, 800 G l, 800 G 1, 800 G l, 800 G 1, 800 G 1, 800 G 1, 800 G 1, 800 N G 1, 600 F-P 1, 800 N G 1, 800 N-G 1, 800 G 1, 800 G 12.5Al2;5Zr 1, 800 N-G 8.25A1,-,42.5V G r G and also by additions of certain alpha-stabilizingelements,

It will be seen that, whereas the Ti-lOAl alloy has only an F-P, i.e., fair-to-poor rating in hot rollability, the addition of 0.25% carbon increases the rating to F-G, i. e., fair-to-good, while the addition of 2.5% zirconium or germanium, or of practically all of the various beta promoters, increases the hot rollability rating to G, i.e., good or excellent. It will further be noted from this data, that although as above stated, the Ti-Al binary alloys cannot be hot worked above about 12% aluminum, at which aluminum level the fabricability is extremely poor, addition of such beta promoters as copper and manganese, impart excellent hot rollability at the 12% aluminum level and even up to thereof.

Although, as above stated, the TiAl binary alloys may be hot worked with up to about 12% aluminum, the thus fabricated material has at room temperature no measurable ductility and an extremely low tensile strength of less than 40,000 p.s.i. Additions of various alpha and/or beta promoters aforesaid, in addition to enhancing the hot workability of the binary alloy, also impart greatly enhanced strength and ductility to the resulting hot worked alloy. This is shown by the room temperature mechanical properties given in the following Table II, for representative alloys as fabricated in accordance with Table I and thereafter annealed.

TABLE II Room temperature mechanical properties of hot workable Ti-Al and TiA1X alloys containing over p 8% A1 in the condition as rolled and annealed Tensile Properties,

p.s.i. X 1,000 Percent Percent Composition, Per- Elonga- Reduc- Hardcent (Balance tion 11 ness,

Titanium) 0.2% Ultimate in 1" Area VHN Ofiset Strength Yield 1 10Al-0.25C 124 0 1 419 10A1-2.5Fe I 113 4 4 421 10Al-2Mn 137 5 5 402 10Al-5Mn 136 0 0 364 12.5Al-5Mn 107 2 4 337 10Al2.5Mo. 178 4 3 388 8.25Al46.7V 134 10 27 317 10Al-2.5Ge 155 3 14 402 10Al-2.5Ge L 114 5 8 346 10A1-4Cu 103 0 0 406 IOAI-GC 115 407 e As quenched from 975 C. b As annealed at 850 C. As quenched from 950 C.

are converted into strong, ductile and fabricable alloys which, being relatively light in weight by virtue of the high aluminum content, are of great industrial utility, particularly for airplane structural members and certain engine components.

The alloying additions aforesaid also increase the as cast strength of the binary Ti-Al alloys as shown by the data in the following Table III.

4 TABLE III Room temperature mechanical properties of TiA1 and TiA1X alloys containing over 8% Al in the as cast condition Tensile Properties,

p.s.i. X 1,000 Percent Percent Composition Per- Elonga- Redue- Hardcent (Balance tion tion ness,

Titanium) 0.2% Ultimate in 1 in Area VHN Offset Strength Yield 82 0 0 309 10 0 0 345 26 0 0 349 40 0 0 431 250 42 0 0 364 40 0 0 418 127 0 0 418 15Al-2 5M 435 15A12.5Fe 70 O 0 374 15Al-2.5Mn 60 0 O 354 As will be seen from the above data, whereas the Ti--l5Al binary alloy has an as cast tensile strength of but 10,000 p.s.i. this is increased 40,000 p.s.i. and even up to as much as 130,000 by the beta promoter additions shown.

The beta promoter additions aforesaid also impart excellent elevated temperature tensile properties to these high aluminum-bearing Ti--Al base alloys as shown by the data in the following Table IV.

TABLE IV Tensile properties at 1000 F. of Ti-(8-I2) Al alloys Tensile Properties,

p.s.LX 1,000 Percent Percent Composition, Percent Elonga- Reduc- (Balance Titanium) tion tion in 0.2% Ultimate in 1" Area Offset Strength Yield 88 20 87 126 30 53 93 118 60 74 64 107 5 15 43 81 5 5 10Al-5Ni 59 79 15 30 The alloys of the above table were annealed prior to testing for mechanical properties at 1000 F.

I have found, as above stated, that the binary alloys containing as much as 12% aluminum, can be fabricated by hot working and that these also have very desirable hot hardness properties. For example, an alloy containing 12% aluminum, balance substantially all titanium, showed average Vickers hardnesses at various temperatures as shown in the following Table V.

TABLE V Temperature, 0. Maximum Vickers Hardness Minimum Average In the test data of Table V, the specimens were hot rolled at 1050" C. to at 28% cross-sectional area reduction, and then annealed for two hours in air at 1000 C. and the surface cleaned and polished prior to hardness testing. The improvement over substantially pure titanium is very marked, the latter having for example, a Vickers hardness of not over 14 at 800 C., as com- Ti12Al alloy at this temperature.

The alloys aforesaid containing beta promoter additions up to about 12 or 14% in general have a mixed alpha-beta microstructure as quenched from the beta field, while those containing upwards of about 15% of total beta promoter content, in general have a substantially all-beta structure as thus quenched. As shown by the Ti-AlV analyses in the above Table I, the improvement in strength combined with high ductility imparted to these high aluminum, titanium base alloys, is much greater where the beta promoter content is sufficiently high to impart an all-beta structure as quenched, than for lower beta promoter additions imparting a mixed alpha-beta structure.

The alloys of the invention were prepared by are melting in a cold mold furnace in an inert or argon atmosphere.

What is claimed is:

1. An alloy consisting essentially of: from more than 8 to 15% aluminum, up to 0.3% carbon, about 0.5 to 50% of at least one beta promoting element but not to exceed 15% in total amount of eutectoid beta promoting elements, balance substantially titanium, characterized in being hot workable and in having a minimum tensile strength of about 100,000 p.s.i., as hot worked and annealed.

2. An alloy consisting essentially of: from more than 8 to 15% aluminum, up to 0.3% carbon, about 0.5 to 50% vanadium, balance substantially titanium, characterized in being hot workable and in having a minimum tensile strength of about 100,000 p.s.i. and a minimum tensile elongation of about 2%, as hot worked and annealed.

3. An alloy consisting essentially of: from more than 8% to about 15 aluminum, up to about 0.3% carbon, up to about 50% of beta promoting elements but not to exceed 15% in total amount of eutectoid beta promoting elements, up to about 5% each of silver, and germanium, balance substantially titanium, characterized in being hot workable at about 1800 F.

4. An alloy consisting essentially of: from more than 8% to about 15 aluminum, about 0.5 to 12% copper, balance substantially titanium, characterized in being hot workable at about 1700l800 F., and in having at 1000 F., a tensile strength of at least 100,000 p.s.i., and a tensile elongation of at least 5%.

5. An alloy consisting essentially of: from more than 8% to about 15 aluminum, about 0.5 to manganese, balance substantially titanium, characterized in being hot workable at about 1800 F., and in having in the hot worked and annealed condition, a tensile strength of at least 100,000 p.s.i. and a tensile elongation of at least 2%.

6. An alloy consisting essentially of: from more than 8% to about 10% aluminum, about 0.5 to 5% germanium, balance substantially titanium, characterized in being hot workable at about 1800 F., and in having a tensile strength of at least 100,000 p.s.i. and a tensile elongation of at least 2%.

7. An alloy consisting essentially of: from more than 8% to about 10% aluminum, about 0.5 to 5% of metal of the group cobalt and nickel, balance substantially titanium, characterized in being hot workable at about 1700-1800 F., and in having a tensile strength at 1000 F. of about 80,000 p.s.i. and a tensile elongation of at least 5%.

8. An alloy consisting essentially of: from more than 8% to about 10% aluminum, about 0.5 to 50% vanadium, balance substantially titanium, characterized in being hot workable at about 1700-1800 F.

9. An alloy consisting essentially of: from more than 8% to about 10% aluminum, about 15 to 50% vanadium, balance substantially titanium, characterized in being hot workable at about 1700-1800 F., and in having a substantially all-beta structure as quenched from the beta field, a tensile strength of at least 100,000 p.s.i. and a tensile elongation of at least 2%, in the hot worked and annealed condition.

10. A cast alloy consisting essentially of: from more than 8% to under 34% aluminum, about 0.5 to 5% of at least one beta promoting element, balance substantially titanium, characterized in having a tensile strength of at least 40,000 p.s.i.

11. An alloy consisting essentially of: from more than 8% to about 12% aluminum, balance substantially titanium, characterized by high hot hardness at temperatures up to about 800 C., and in being hot workable at about 1050" C.

12. An alloy consisting essentially of: from more than 8% to about 10% aluminum, about 0.5 to 5% molybdenum, balance substantially titanium, characterized in being hot workable at about 1700-1800 F.

13. An alloy consisting essentially of: from more than 8% up to 34% aluminum, up to 50% of isomorphous beta promoters for aluminum contents up to 15%, up to 15 of eutectoid beta promoters for aluminum contents up to 15 up to 5% each of germanium and silver for aluminum contents up to 15%, up to 0.3% carbon, and the balance substantially titanium, characterized by an ultimate strength of at least 40,000 p.s.i.

References Cited in the file of this patent UNITED STATES PATENTS 2,370,289 Chandler Feb. 27, 1945 2,464,836 Thomas Mar. 22, 1949 2,550,447 Blumenthal Apr. 24, 1951 2,554,031 Jaifee et al. May 23, 1951 2,578,098 Southard Dec. 11, 1951 2,596,486 Jafi'ee May 13, 1952 2,703,278 Finlay et al. Mar. 1, 1955 2,711,960 Methe June 28, 1955 2,754,205 Jafiee et al. July 10, 1956 FOREIGN PATENTS 681,143 Germany Sept. 15, 1939 679,705 Great Britain Sept. 24, 1952 

1. AN ALLOY CONSISTING ESSENTIALLY OF: FROM MORE THAN 8 TO 15% ALUMINUM, UP TO 0.3% CARBON, BOUT 0.5 TO 50% OF AT LEAST ONE BETA PROMOTING ELEMENT BUT NOT TO EXCEED 15% IN TOTAL AMOUNT OF EUTACOID BETA PROMOTING ELEMENTS, BALANCE SUBSTANTIALLY TITANIUM CHARACTERIZED IN BEING HOT WORKABLE AND IN HAVING A MINIMUM TENSILE STRENGHT OF ABOUT 100,000 P.S.I., AS HOT WORKED AND ANNEALED. 